/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j.helpers;

import java.util.Calendar;
import java.util.TimeZone;
import java.util.Date;
import java.text.FieldPosition;
import java.text.ParsePosition;

// Contributors: Arndt Schoenewald <arndt@ibm23093i821.mc.schoenewald.de>

/**
 * Formats a {@link Date} in the format "yyyy-MM-dd HH:mm:ss,SSS" for example
 * "1999-11-27 15:49:37,459".
 * 
 * <p>
 * Refer to the <a href=http://www.cl.cam.ac.uk/~mgk25/iso-time.html>summary of
 * the International Standard Date and Time Notation</a> for more information on
 * this format.
 * 
 * @author Ceki G&uuml;lc&uuml;
 * @author Andrew Vajoczki
 * @since 0.7.5
 */
public class ISO8601DateFormat extends AbsoluteTimeDateFormat {
	private static final long serialVersionUID = -759840745298755296L;

	public ISO8601DateFormat() {
	}

	public ISO8601DateFormat(TimeZone timeZone) {
		super(timeZone);
	}

	static private long lastTime;
	static private char[] lastTimeString = new char[20];

	/**
	 * Appends a date in the format "YYYY-mm-dd HH:mm:ss,SSS" to
	 * <code>sbuf</code>. For example: "1999-11-27 15:49:37,459".
	 * 
	 * @param sbuf
	 *            the <code>StringBuffer</code> to write to
	 */
	public StringBuffer format(Date date, StringBuffer sbuf,
			FieldPosition fieldPosition) {

		long now = date.getTime();
		int millis = (int) (now % 1000);

		if ((now - millis) != lastTime) {
			// We reach this point at most once per second
			// across all threads instead of each time format()
			// is called. This saves considerable CPU time.

			calendar.setTime(date);

			int start = sbuf.length();

			int year = calendar.get(Calendar.YEAR);
			sbuf.append(year);

			String month;
			switch (calendar.get(Calendar.MONTH)) {
				case Calendar.JANUARY :
					month = "-01-";
					break;
				case Calendar.FEBRUARY :
					month = "-02-";
					break;
				case Calendar.MARCH :
					month = "-03-";
					break;
				case Calendar.APRIL :
					month = "-04-";
					break;
				case Calendar.MAY :
					month = "-05-";
					break;
				case Calendar.JUNE :
					month = "-06-";
					break;
				case Calendar.JULY :
					month = "-07-";
					break;
				case Calendar.AUGUST :
					month = "-08-";
					break;
				case Calendar.SEPTEMBER :
					month = "-09-";
					break;
				case Calendar.OCTOBER :
					month = "-10-";
					break;
				case Calendar.NOVEMBER :
					month = "-11-";
					break;
				case Calendar.DECEMBER :
					month = "-12-";
					break;
				default :
					month = "-NA-";
					break;
			}
			sbuf.append(month);

			int day = calendar.get(Calendar.DAY_OF_MONTH);
			if (day < 10)
				sbuf.append('0');
			sbuf.append(day);

			sbuf.append(' ');

			int hour = calendar.get(Calendar.HOUR_OF_DAY);
			if (hour < 10) {
				sbuf.append('0');
			}
			sbuf.append(hour);
			sbuf.append(':');

			int mins = calendar.get(Calendar.MINUTE);
			if (mins < 10) {
				sbuf.append('0');
			}
			sbuf.append(mins);
			sbuf.append(':');

			int secs = calendar.get(Calendar.SECOND);
			if (secs < 10) {
				sbuf.append('0');
			}
			sbuf.append(secs);

			sbuf.append(',');

			// store the time string for next time to avoid recomputation
			sbuf.getChars(start, sbuf.length(), lastTimeString, 0);
			lastTime = now - millis;
		} else {
			sbuf.append(lastTimeString);
		}

		if (millis < 100)
			sbuf.append('0');
		if (millis < 10)
			sbuf.append('0');

		sbuf.append(millis);
		return sbuf;
	}

	/**
	 * This method does not do anything but return <code>null</code>.
	 */
	public Date parse(java.lang.String s, ParsePosition pos) {
		return null;
	}
}
